Certain technical standards with which each cable television system should comply have been established. One such performance standard is that the ratio of visual signal level to system noise shall not be less than 35 decibels.
In accordance with the practice of the prior art, this signal-to-noise ratio has been measured by first measuring the noise on an unused cable television channel or by turning off the signal on the channel where the noise was being measured. The latter procedure is generally used where the cable system is crowded. The strength of the television video signal on one of the used channels is also measured, and the signal-to-noise ratio is then calculated using the results of these two measurements.